Getting one single entry from model via ajax

[Stéphane Manguette]

Hello Django community,

I'm pretty new to Django and I'm getting stuck on the following issue. 

I have a model defined as follows :

class temp_db(models.Model):

date = models.DateTimeField()

tempext = models.DecimalField(max_digits=4, decimal_places=2)

tempeau = models.DecimalField(max_digits=4, decimal_places=2)

humid = models.DecimalField(max_digits=4, decimal_places=2)

def __str__(self):

return str(self.date)

temp_db is being update every two minutes with a new entry thanks to a dedicated python script.

I'm trying to develop a website page which would constantly show the last value recorded in the table temp_db.

I would like to use ajax to retrieve the last entry (and you will understand : without refreshing my webpage)

I've been consulting many tutorials to understand ajax and I think I'm pretty ok with the way to do that from the client side.

From a django standpoint; I'm getting trouble in transferring the last entry of my table to the client. I think that json could help me but when I'm trying to convert my entry into json with the following view code...

def myview1(request):

end_range = datetime.now()

range = timedelta(days=1)

beg_range = end_range - range

chart = temp_db.objects.filter(date__gte=beg_range)

last_entry = chart.latest('date')

data = serializers.serialize('json', last_entry)

return JsonResponse(data, safe=False)

...Django returns the following error :

Internal Server Error: /myview1/

Traceback (most recent call last):

  File "/home/pi/.virtualenvs/django/local/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner

    response = get_response(request)

  File "/home/pi/.virtualenvs/django/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response

    response = self.process_exception_by_middleware(e, request)

  File "/home/pi/.virtualenvs/django/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response

    response = wrapped_callback(request, *callback_args, **callback_kwargs)

  File "/home/pi/Projects/dashboard/views.py", line 55, in myview1

    data = serializers.serialize('json', last_entry)

  File "/home/pi/.virtualenvs/django/local/lib/python2.7/site-packages/django/core/serializers/__init__.py", line 129, in serialize

    s.serialize(queryset, **options)

  File "/home/pi/.virtualenvs/django/local/lib/python2.7/site-packages/django/core/serializers/base.py", line 80, in serialize

    for count, obj in enumerate(queryset, start=1):

TypeError: 'temp_db' object is not iterable

I guess that the problem is that one single entry is trying to be serialized since when I'm trying to serialize temp_db.objects.all(). -> it works. Maybe json is not the the way to do this but the only thing I would like to do is to properly get my object from a client side and use it like Myentry.tempext in the Js code of the client webpage

Thanks in advance for your help.

Stéphane

[ANi]

You need to make it iterable, so there are two ways to do it.

One is to let it become a list with single object while another one is to use filter so the result will be a QuerySet.

In your case will be the first one.

Stéphane Manguette於 2019年1月15日星期二 UTC+8上午9時26分14秒寫道：